This invention relates to a method and an apparatus for forming replicas of body parts. More particularly, this invention relates to a method of using a reusable apparatus to form molds of body parts from molding materials containing alginate and casting accurate replicas of the body parts.
Life-size, accurate replicas of body parts are used in a variety of fields, including medicine, art, and education. The conventional method of forming such replicas involves, first, forming a mold of the desired body part, for example of a leg, by wrapping the leg with plaster bandages, permitting the plaster to harden, cutting the bandages, and then prying the bandages away from the leg. The plaster bandages are then used as a mold for casting a replica of the leg, after which the bandages are removed and discarded. One problem with this is that when the plaster bandages are removed from the leg of a patient or model, there is necessarily some distortion of the plaster and this results in a replica which is not exactly the same shape as the leg being modeled. Further, preparing the bandages, wrapping them about the body part, and then removing them is both time-consuming and messy. Finally, after the replica is cast, the plaster bandages must be discarded, being unsuitable for repeating the casting process. The process is thus wasteful of time, materials, and effort.
One proposal for improving the conventional plaster bandage method of constructing molds involves encasing the body part with padding material, coating the padding material with petroleum jelly to prevent adhesion, and wrapping the padded body part with plaster bandages (U.S. Pat. No. 4,735,754). After the plaster drys and hardens, the plaster bandages are cut and removed from the padded body part, then the padding material is removed and the body part is placed in the plaster bandage again. Alginate or other molding material is poured into the plaster form and permitted to set. The body part is then removed, leaving an impression of the body part in the alginate mold. This system of forming molds suffers from several disadvantages. First, the plaster form is not reusable, thus, if a mold of a different patient or model were desired, a new plaster form would need to be constructed. Second, this process is clumsy and time-consuming. The patient or model must endure two casting procedures: (1) being wrapped in padding material, having the plaster bandages applied, waiting for the plaster to dry and harden, and having the plaster form being removed, and (2) casting the alginate impression. Third, the system relies on custom-fitting the plaster form for each individual patient or model. Fourth, the system is less useful for making molds of an entire leg than of a mere foot. This is due to the cracks and distortions that are introduced in the plaster form in removing it from the padded body part. The problems with cracks and distortions increase as the size of the body part increases. Since the alginate impression also relies on the plaster form or general support and shape, the accuracy of the alginate impression depends on the plaster form. Fifth, a plaster form for making a mold of an entire leg would need to be thick enough to support the 25-40 pounds of alginate used in making the impression. Increased thickness of the plaster form would require more time to dry and harden. Further, a thick plaster form would be more susceptible to cracking and distortion in removal from the padded body part.